Nestjs - define OneToMany relation in entity

Question

I am defining entity fields in my NestJS project. I have ManyToOne realtion that is defined successfully. I have trouble finding the right way to define OneToMany relation to fit the syntax I used for other relation.

import {Entity,Column, PrimaryColumn, ManyToOne,JoinColumn,OneToMany} from "typeorm";
import { Account } from "./account.entity";
import { Balance } from "./balance.entity";
import { BaseEntity } from "./base.entity";

@Entity()
export class MainEntity extends BaseEntity {
  @PrimaryColumn({
    type: "varchar",
    name: "id",
    unique: true
  })
  id: string;

  @ManyToOne(() => Account, { nullable: true })
  @JoinColumn({
    name: "account_id",
    referencedColumnName: "id"
  })
  account: Account;

@OneToMay relation needs to be connected to the Balance entity and mappedBy paymentDevice field in it.

My try:

@OneToMany(() => Balance, ...)
balances: Balance[]

I am in NestJs and typescript so this is challenging for me.

Goss Gowtham Goss Gowtham · Accepted Answer · 2020-07-14T08:50:15

Generally, TypeORM relations used in NestJS are simple and dev-friendly. The code which you've written defines parameters which are already predefined. For example,

@PrimaryColumn({
    type: "varchar",
    name: "id",
    unique: true
  })

This exact parameters is what defined by

@PrimaryColumn() // unique: true
id: string //varchar, name: id

So you can have the code just like below. For Account Entity,

@Entity()
export class Account {

    @PrimaryColumn()
    id: string;


    @ManyToOne(type => Balance, balance => balance.id)
    balance: Balance;

}

For Balance Entity

@Entity()
export class Balance {

   @PrimaryColumn()
   id: string;


   @OneToMany(type => Account, account => account.id)
   @JoinColumn({name: "account_id"})   
   // defining this is also optional because by default,
   // the referenced foreign key is named as <column_name>_id or account_id

   account: Account;

}

This will create a many-to-one relationship on Account and OneToMany on Balance entity. For more such examples, Refer: https://orkhan.gitbook.io/typeorm/docs/many-to-one-one-to-many-relations

Nestjs - define OneToMany relation in entity

1 Answers